Neddylation is critical for cardiomyocyte maturation by promoting perinatal metabolic transition

Abstract

The heart undergoes significant structural, metabolic, gene expression and functional alterations during the perinatal to postnatal transition. Although recent studies have delineated several novel epigenetic and transcriptional regulators of cardiac maturation, post‐transcriptional mechanisms regulating cardiomyocyte (CM) maturation remain poorly defined. We hypothesized that neddylation, a protein modification that conjugates a small ubiquitin‐like protein NEDD8 to protein substrates via an E1‐E2‐E3 cascade, plays a critical role in driving cardiac maturation program. Taking advantage of an AAV9‐cTnT‐Cre system and the mTmG reporter, we achieved CM‐specific, mosaic knockout of NAE1, a critical neddylation E1 enzyme, in postnatal hearts. Mice with high levels (>90%) of NAE1 deletion in CMs exhibited a cardiomyopathy as evidenced by significant chamber dilatation and greatly compromised cardiac contractility. While mice with modest levels (30%) of NAE1 deletion in CMs had preserved cardiac function, inhibition of neddylation caused severe disruption of transverse tubules (T‐tubules) network and a disturbance in binucleation and cell enlargement in NAE1‐null CMs, as well as upregulation of fetal genes and downregulation of their adult forms, indicating a key, cell‐autonomous role for neddylation in CM maturation. Transcriptome analysis revealed an upregulation of glycolytic genes and a downregulation of oxidative metabolic genes in NAE1‐deficient hearts. Biochemical analyses confirmed defects in fatty acid oxidative metabolism and mitochondrial dysfunction in NAE1‐deficient hearts and neonatal CMs treated with a neddylation inhibitor. Mechanistically, we found that HIF1α, a transcription factor known to promote glycolysis and suppress oxidative metabolism, is a putative NEDD8 target. Inhibition of neddylation stabilized HIF1α and led to abnormal accumulation of HIF1α in NAE1‐deficient hearts and neonatal CMs treated with neddylation inhibitor, which may contribute to the observed metabolic dysfunction. Together, our findings suggest that neddylation serves as a novel post‐translational mechanism regulating CM maturation through sustaining the glycolytic to oxidative metabolic switch in postnatal hearts.